Sensitivity and specificity of intraoperative recurrent laryngeal nerve stimulation in predicting postoperative nerve paralysis

Bilateral recurrent laryngeal nerve (RLN) paralysis after thyroidectomy is infrequent, but serious when it occurs. Intraoperative knowledge of the status of the nerve after dissection could potentially provide the surgeon with important decision-making information. The current study examines the sensitivity and specificity of intraoperative stimulation of the RLN during thyroid surgery for predicting postoperative RLN deficits. Eighty-one RLNs in 55 patients were identified to be at risk of injury during thyroidectomy or parathyroidectomy performed between January 1998 and February 2000. Intraoperative determination of RLN function was evaluated with a disposable nerve stimulator (Xomed, Jacksonville, Florida) set at 0.5 mA. Injury was assessed by palpating for a contraction of the posterior cricoarytenoid muscle while the stimulus was applied. Postoperative assessment of RLN integrity was determined by using indirect or direct laryngoscopy to visualize vocal fold mobility. Nine RLNs failed to elicit a posterior cricoarytenoid contraction after nerve stimulation, and 4 RLNs were determined to be deficient in the postoperative evaluation. The calculated sensitivity and specificity were 75% and 92.2% with a positive predictive value of 33.3% and negative predictive value of 98.6%. The RLN injury rate was 4.94%. We conclude that intraoperative RLN stimulation is a relatively safe and useful method of determining what RLN function will be after thyroid or parathyroid surgery.